A yellow precipitate was then thrown down, as you perceive
is the case now; and this, carefully washed and cleansed, gave us that
body [pointing to a specimen of the chloride of platinum and ammonium],
the other elements, or nearly all, being ejected. This substance being
heated, gave us what we call platinum sponge, or platinum in the metallic
state, so finely divided as to form a kind of heavy mass or sponge, which,
at the time that Dr. Wollaston first sent it forth, was not fusible for
the market or in the manufacturers' workshops, inasmuch as the temperature
required was so high, and there were no furnaces that could bring the mass
into a globule, and cause the parts to adhere together. Most of our metals
that we obtain from nature, and work in our shops, are brought at last
into a mass by fusion. I am not aware that there is in the arts or
sciences any other than iron which is not so. Soft iron we do not bring
together by fusion, but by a process which is analogous to the one that
was followed in the case of platinum, namely, welding; for these divided
grains of spongy platinum having been well washed and sunk in water for
the purpose of excluding air, and pressed together, and heated, and
hammered, and pressed again, until they come into a pretty close, dense,
compact mass, did so cohere, that when the mass was put into the furnace
of charcoal, and raised to a high temperature, the particles, at first
infinitely divided--for they were chemically divided--adhered the one to
the other, each to all the rest, until they made that kind of substance
which you see here, which will bear rolling and expansion of every kind.
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